The present disclosure relates generally to methods for preparing biomaterial compositions and methods for using the biomaterial compositions. More particularly, the present disclosure relates to hydrogel compositions, and particularly hydrogel arrays, methods for screening cell substrate interactions using the hydrogel compositions, and methods for promoting tubulogenesis using the hydrogel compositions.
The development of most tissue types involves a complex interplay of multiple signals leading to controlled precursor cell differentiation into mature, tissue-specific cell types. For example, mesenchymal stem cells (MSCs) may be differentiated in vitro into osteoblasts, chondrocytes, myoblasts, adipocytes, neurons, and endothelial cells by exposure to a variety of growth factors. Exposure to growth factors may be controlled by the media and the substrates upon which the cells are cultured. Substantial progress has been made in the development of defined media, but only more recently has the role of substrates and cell-substrate adhesion on cell growth been examined.
Based on studies to determine defined media, it has become apparent that the substrate is important for successful cellular growth and tissue generation. For example, it has been demonstrated that attachment to the substrate by human embryonic stem cells may contribute to the variability in whether the cells remain undifferentiated or undergo differentiation. Therefore, it is important to not only identify cell culture media for successful cell culture conditions, but to also identify defined substrates.
Screening well-defined surfaces in an array format allows rapid identification of specific molecules that promote cellular adhesion, cellular spreading, proliferation, migration and differentiation, as well as molecules that regulate cell behavior. Biomaterial arrays such as self-assembled monolayers (“SAMs”) in array formats (i.e., SAM arrays) have been constructed that present ligands to cells plated onto the array. A SAM is an organized layer of amphiphilic molecules in which one end of the molecule exhibits a specific, reversible affinity for a substrate and the other end of the molecule has a functional group. Because the molecule used to form the SAM array is polarized, the hydrophilic “head groups” assemble together on the substrate, while the hydrophobic tail groups assemble far from the substrate. Areas of close-packed molecules nucleate and grow until the surface of the substrate is covered in a single monolayer.
The use of alkanethiols to construct SAM arrays allow for the formation of reproducible SAM arrays and surfaces. SAM arrays may be used to identify specific ligands or epitopes that promote cellular attachment, spreading, proliferation, migration and differentiation. Additionally, SAM arrays may be patterned such that ligands will be presented to the cells in defined areas of the array.
While biomaterial arrays such as SAM arrays provide an excellent model substrate for investigating the effects of an immobilized ligand on cell behavior, preparing SAM array platforms using less labor intensive processes are needed to make SAM array use more widespread. Accordingly, there exists a need for alternative methods for preparing patterned biomaterial arrays to identify surfaces that will support survival and growth of cells in culture, allow rapid identification of specific molecules that promote cellular adhesion, cellular spreading, proliferation, migration, differentiation and regulate cellular behavior.